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(No Model.) 3 Sheets-Sheet i.

J. G. STATTER.

METHOD OF DETERMINING THE SHAPE OF POLE PIECES FOR DYNAMOS.

No. 410,656. Patented Sept. 10, 1889.

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(No Model.) 3 Sheets-Sheet 2.

J. G. STATTER. METH ODOF DETERMINING THE SHAPE OF POLE PIECES FOR DYNAMOS.

Patented Sept. 10,1889

FIG.56L.

(No Model.) 3 Sheets-Sheet 3.

J. G. STATTER;

METHOD OF DETERMININGTHE SHAPE OF POLE PIECES FOR DYNAMOS.

No. 410,656. Patented Sept. 10, 1889.

FIG I FIG 6.

UNITED STATES PATENT OFFICE.

JOHN GRICE STATTER, OF LONDON, COUNTY OF MIDDLESEX, ENGLAND.

METHOD OF DETERMiNlNG THE SHAPE OF POLE-PlECES FOR DYNAMOS.

SPECIFICATION forming part of Letters Patent No. 410,656, dated September 10, 1889.

Application filed March 26, 1889. Serial No. 304,543. (No model.) Patented in England February 23, 1887, No. 2,825; in Belgium February 2, 1888, No. 80,487: in France April 13, 1888, No. 188,498, and in Spain May 14, 1888, No. 7,943.

1887; Belgium, No. 80,487, dated February 2,

1888; France, No. 188,498, dated April 13, 1888, and Spain, libro 6, folio 243, numero 7,943, dated May 14:, 1888;) and I do hereby declare that the following is a full, clear, and

exact description of the invention, which will enable others skilled in the art to which it appertains to make and use the" same.

These improvements have for their object, in the case wherein themachinc is used as a generator, the maintenance of a constant current through a variable resistance, or a constant current or electro-motive force when the machine is driven atvarying speeds, and,

d in the case wherein the machine is'used as amotor, the varying of the mechanicalenergy given out. In obtaining such objects these improvements require the position of the brushes on the commutator to be altered, and they enable such brushes to be moved round the commutator through a large angular dis tance-say ninety dcgreeswithout the production of sparking. I do not herein specify any particular means whereby the brushes are moved. They can be moved by hand or any suitable ku'own automatic'device.

'In carrying theprinciples of my invention into elfect for'the purpose of obtaining a machine capable of acting as above mentioned, 'I'find it necessary to maintain constant the product of the magnetic intensity aifecting those coils of the armature which are at any;

moment passing under the brushes expressed in any suit-able units-such, for example, as gram, centimeter, second units and the length of the conductor of such coils as is directly acted upon by the field-magnets expressed, say, in centimeters. This magnetic intensity-must be of a certain value, as'the following explanation 'will -show. For the purpose of this explanation I shall assume that I employ an armature of the drum or ring type and field-magnets such as those 1 shown in the accompanying drawings, it being understood that'the accompanying draw behind to one immediately in front of the brushes experiences a sudden reversal of the current'which it is carrying. This causes a momentary electro-motive force of self-induction to take place in the said coil, which, if not neutralized, will cause a current to leap between that plate of the commutator connected to the coil which has just passed from under a brush and the brush which the plate has just leftiu other words, sparking is produced. By so placing the brushes that the magnetic intensity of the field-magnets shall afiect this coil to a suitable extent this electro-motivc force is neutralized by the electromagnetic induction on this coil.

In order to be able to move the brushes through a large angular distance-say ninety degrees around the commutator without producing sparking, it is necessary that the inductive eifect' of the field-magnets upon that part of the armatur upon which the coils passing under the brushes are wound shall be constant throughout such angular distance, and shall be sufiicient to neutralize the GlGCiLl'0-lll0l3lV6 force of self-induction hereiubefore referred to.

readily understood, I shall refer to the ac "In 'orderthat; my'invention may be more companying drawings, making a partof this specificatiomand shall first describe how I carry it into efiect in the case of a dynamoelectric machine or generator; and thereafter I shall describe how I carry it into effect in the case of an electro-dynamic machine or motor. I am now using the words dynamoelectric and electro-dynamic in their'narrow and specific sense.

Figure 1 is a diagram of the current curves generated in the armature under the conditions set forth. Fig. 2 is an isometric view of a pole-piece incised in accordance with my Inconstructing myimproved machine to act as a generator, say, for. the production of" I a high-tension current of ten amperes, at a opera ion,

. (which-a maximumelectro-motiveforoeoftwothousand volts, I employa quantity of iron relatively large to the quantity of wire in both the'field magnets Q U. and the armature S, and'havinga depth of armature-core, say, three to fourtimes the depth of the external winding on the same, and having in the field-magnets a mass of iron (preferably wrought-iron) considerably in excess of the massof the iron in the armature S. Having constructed such a machine with a ring-armature S in the usual way.-that is, so as to have the polepieces P P, which are united by a yoke R, solid and concentric with the armature and with just sufficient clearance between the pole-tiiecesand the armature-I put it into and close the circuit I through such a resistancefor instance, the lights Grv G-as will enable the machine to give out its norma current, andI set the brushes T '1" at the position where no sparking occurs. I now take an apparatus, which I may for convenience term an exploring apparatus, and which consists of a voltmeter V of any convenient type, with flexible conductors l l'attached thereto, which flexible conductors terminate at their other extremities in two small brushes or plates t t of metal, insulated from one another and suitably distanced apart. With this apparatus I obtain relative indications of the electro-motive force of the current 7 re also relative indications of the re- 'snlta'nt magnetic intensity produced by the mutual action upon each other of the field-magnets and. the armature) flowing through the I coils, Whose circuitI complete by means of the exploring apparatus; and thisI do bybringin g I the magnetic intensity.

the brushes of. the exploring apparatus (hereinafter for the sake of conveniencetermed the exploring-brushes) incontact with adjacent segmentsof it must be understood, is revolving at the time and the machine giving out its normal current. ..The object of obtaining such indications is to enable me to alter the shape of i f at which the machine is driven and the resisti ance of the said external circuit being main- 7 'ttained constant.

the pole-pieces P P in such a way that when the pole-pieces are so altered the-product ot' atfecting'those coils of the armature which are at any moment passing under the brushes into the length'of the conductor of such coils as is directly acted upon by the field-magnets shall be constant. This alteration I effect by incising or boring the pole-pieces, so as to produce orifices or cavities II II of certain definite shape and size, such shape and size being determined in the manner following: I determine the shape by plotting out theelectro-motive forces in,-

the commutator W, whicli,

. obtained plotted out in curves, as shown in Fig. 1, the main brushes in connection with the external circuit remaining in the same podicated by the voltmeter 'V "ofthe exploring apparatus- I set out such electro -motive forces as ordinates, and as, abscis'szelset out the angular distances corresponding'with the positions which the. exploring-brushes t t at the time of a reading being obtained upon the voltmeter occupy upon the commutator.

These angular distances are set out from] 1 vertical line midway. between the poles, an

are diagrammatically represented in .Fig. 3-, where itwill be seen that angular distances equal'to forty-five degrees are marked passing in the direction of the arrow. It will be noticed that these angular distances are represented as an gles from 0 to 180 on one side of the said vertical line, and repeated as 0 to 180. on the. other side. In this figure the exploring-brushes t t are shown in connection with the voltmeter V and .in contact with commutator-segments W at an angle of twenty degrees from the part where the said vertical line cuts the top of the. armature s,

"the main brushes T T',.-that is, the brushes connected with the external circuit I fed by the machine-being one at this point,iand the other at the corresponding angular distance from the part where the vertical line cuts the bottom of the armature and diametrically opposite, these being the positions which the brushes would naturally occupy iri a ma-- chine as usually constructed. In the immediately preceding sentence I mention that the exploring-brushes it are at the same point as the main brushes T T. This is not strictly correct, since no reliable readings can be obtained by the exploring apparatus when the exploring-brushes are exactly in line with the main brushes, on account of the continual shortcircuiting of adjacent sections of the commutator by the main brushes. I therefore take readings with the exploring-brushes immediately behind and immediately before the main brushes, and am able to draw'the curve hereinafter described with sufficient accuracy "without having taken a reading exactly under the main brushes. The electremotive force at this 'angleis thus obtained, and electro-motive forces are similarly obtained at all the whole of the commutator being exparts,

for this purpose, and the indications plored.

sition during such exploration, and the speed Referring to Fig. 1, it will be seen that O C G 0 show a curve of electro-motive forces as obtained by exploring the whole commutator.

- of the main brushes to sixty degrees, and in the same manner plot out the curve D D D Di roq Again, I shift the main brushes to an angle of ninety degrees and obtain the indications last case.

which enable me to plot out the curve E EE E. Upon the curves, as shown in Fig. 1, O C on the curve C C O 0 represent the positions of the main brushes when they are at an angle of twenty degrees. The points D D on the curveD D D D represent the positions of the main brushes when they are at an angle of sixty degrees, andthe points E E on,

the curve EE E E represent the positions of the main brushes when they are at an angle of ninety degrees. It will be seen that when the main brushes are in the'positions shown on the curve C C O 0 there is no sparking. When in the positions shown on the curve D D DD, it will be seen that there is sparking, the electro-motive force in the coil short-circuited by the main brushes being represented by the length of the ordinate L, (this ordinate being obtained as hereinbefore described,) which electro-motive force represents the excess of the inductive effect, as hereinbefore mentioned, over the self-inductive efiect in the coil passing under the brushes at the time of observation, Similarly in the case of the curve E E E E, it will be seen that there (this ordinate being obtained as herein described) representing this, as described in the In Fig. l I hav e only plotted out three curves, these being representations of results obtained during explorations with the brushes in three different positions. 7 In practice, however, instead of making three explorations, I make a considerable numbersay ten or twelveand plot the curves obtained by this means in the samemanner as are those shown in Fig. 1. These curves I shall call, for the purpose of this specification, exploration-curves. These exploration-curves I utilize to obtain a new'curve,

which, for convenience, I shall hereinafter refer to astheshaping-curve. Thesha'ping curve is obtained as follows: On the horizontal line (see- Fig. 1) and at the pointcor responding with the angle at which the main brushes are at the time when the explorationcurve C C 0-0 is obtained, I set up an ordinate cutting the said exploration-curve C O G. C. On the horizontal line, and at the point corresponding with the angle at which the main brushes are hen the exploration-curve 'D D D D is obtained, I set up the ordinate L,

cutting said exploratiomcurve D'D D D5 0n the horizontal lineand atthe point corresponding with.- the angle at which the main brushes are when the exploration-curve E E E E is obtained, Iset up the ordinate K,,cutting the said exploration-curve E E, E E. These. three points 0', D, and E, I join by a line and so obtain the shaping-curve J desired,'it being of course understood that to obtain, such a shaping-curve as would be desirable in practice, instead of having only three curves, (the result of explorations in three positions of the main brushes,) I should,

as before mentioned, plot out a large number of curves and so obtain additional points, by the connection of which I would obtain my desired shaping-curve. This shaping-curve represents the excess of the inductive effect,

as hereinbefore mentioned, over the self-inductive effect in the'coil passing under the main brushes at different positions, of these with respect to the before-mentioned vertical line. This curve also indicates where and to what extent the magnetic intensity of the field exceeds the definite value hereinbefore referred to. I therefore utilize such indications as are shown by the shape of this curve to guide me indetermining the shape of a part of the metal of the pole-pieces to be removed, as hereinbefore mentioned.

To determine the amount of metal to be re moved or the size of the cavities or orifices to be made, I have recourse to experiment, as I know of no definite method approaching accuracy by which I can obtain this information. A rough guide, however, exists in the -length of the ordinates which represent. the excess of the inductive effect over the selfinductive effect, as before mentioned. is sparking at the brushes, the ordinate K I shall now proceed to explain] how Iemploy the information yielded by the shape of this shaping-curve to guide me in altering the former y pole-pieces. For this purpose I shall firstof all refer to one form of modified pole-piece-namely, that in which a groove is cut parallel to the armature-shaft N and thereafter I shall refer to other forms of modified pole-pieces which may be constructed according to myiuvention. Having obtained the shaping curve, as before mentioned, I proceed to cut out grooves H H in the pole-pieces P, P of'a shape resembling ;that of the shaping-curve and in a direction ,parallel to the armature-shaft N. Such a @groove is represented in Fig. 2, the position got the said groove being indicated by the shape .of the curve andcorresponding with the angles, as shown in Figs. 1 and 3. Having'cut out this groove'as aforesaid, I replace the armature and run the machine again, using the exploring apparatus and again plotting out curves, as before. In order not to confuse the diagram shown in Fig. 1 by having too, many curves, Irepresent onlyone exploration-cu-rve, obtained after the removal of some of the iron from the pole-pieces, and this exploration-curve, which is taken with the main brushes at an angle of ninety degrees with the vertical line above referred to, is shown in the dotted line F. It will be seen that this new exploration-curve cuts the ordinate K corresponding with the angular position of the brushes on the horizontal line, and

obtain the desired purpose. If, however, it had not been so, it would have been necessary to alter the groove in accordance with this second shaping-curve, and then to obtain another shapingscurve, and so alter the groove as to (make it correspond therewith, and so on, shaping-curves being obtained and the grooves altered in accordance therewith until it were found that the machine could be run as before mentioned and curves be taken which s'hould out on the horizontal line the ordinates cmresponding with the positions of the main bruihesat all angular positions. Figs. 2, 3, and 3 illustrate pole-pieces modified in the manner'just describedthat is, so

as to have grooves cut in them in a direction parallel to the armature-shaft and incised in accordance with the form of the shaping curve.

Having. now-described .my method of determining the shape of one formv of modified pole-piece namely, that in which a groove is ,cut parallel to the armature shaftI shall proceed to describe some otherforms ofmodified pole-pieces-that is to say, pole-pieces modified by the formation of cavities or orifices difiering. from theform just described.

A large number of such modifications "could be made, and I desire it tobe understood that I donot' limit myself to any particular form of cavity or orifice H- H, as theessence of my invention. consists in the modification-of. the pole-pieces by the formation of cavities or orifices, for the purpose either of varying the magnetic intensity or of varying the length ofconductor acted upon, as previously mentioned, and in accordance with whatis shown to be necessary by the form of the shaping- Figs. 4, 5, and 6 illustrate pole-pieces modi-' fied indifferent manners. Fig. 4 illustrates a case closelyresembling that hereinbefore described withreference to Figs. 2, 3, and 3,

the difference being that instead of the groove being cut across the whole face of the polepiece, as shown in Figs. 2, 3, and-3, it is cut in an interrupted manner. In the figurenamely, Fig. 4-it will be seen that two cavities H H are out; but if the metal between and at the sides of these cavities were cut away, it will be seen that cavities of the same form would be obtained as in Figs. 2, 3, and

3. Fig; 5 shows anothermodification. In this case an orifice H is bored right through the pole-piece in a direction at right angles to the armature-shaft, and the resemblance between this formof orifice as it would be It is n bored the whole way through, as shown'in the shown in cross-section with the shaping-curve or agroove such as is shown in Fig. 2 will be apparent. At the angular distancewith reference to the commutator where the ordinate is highest (see Fig.1) or the. cavity is deepest (see Fig.2) the orifice of Fig. 5. is broadest.

o necessary that the orifice should be figure. It may be merely a cavity of a shape similar tothe orifice shown; Fig. 6 illustrates another form of pole-piece modified in acoordance with my invention. It'will be seen that this form of modified pole-piece differs from that shown in Fig. 4 chiefly in the fact that the cavities H H, instead of being incised at or near the central part of the.

pole-pieces, are incised at the ends. thereof. It will: be noticed that of these figures illustrating modified forms of pole-pieces, Figs. 2,3, and 3 are the best 'illustrations of the case wherein the magnetic intensity, as previously described, is varied; whereas Fig.

6 illustrates probably in abetter manner than the other figures the 'case'wherein the length of conductor acted upon by the field-magnets is varied. Figs. 4 and 5 may be taken as being good illustrations of cases which are, as it were, a compromise between those illustrated in'Figs. 2 and 6, respectively. Such compromise might be introduced still further inmaking'other forms of modified pole-piece.

For example, a form of pole-piece might be made differing fromthat shown in Fig. 2, in that the grooves might be shallower toward the center than at the ends of the said grooves, or vice versa, and other modifications will readily suggest themselves; I

Having now described the carrying out of my invention as applied to adynamo-electric machine or generator, I shall proceed to describe the carrying out of my invention with regard to its application to..-an electro-dynamic machine or motor.' I commence, as in the case of a generator, by constructing an electromotor after the ordinary manner, and then I proceed to run it and obtain shapingcurves in the same manner as I have alreadydescribed with regard to carrying out my invention in the case of a generator, but with this difference, that instead of: running the machine as a generator I run it as a motorthat is to say, I keep the feeding-current con stant, and alter the position of the -,'main brushes, so as to maintain the speed of revolution constant under a varying load. Having obtained such shaping-curves, I use them for the purpose of guiding me in modifying the pole-pieces exactly as hereinbefore demargin of metal to work upon.

I would remark that. hitherto I have assumed that the com mutator-plates are at the same angular position on the armature as the coils with which they are in connection; but this is not always the case, for in some arma turos the coils, instead of being connected to appear to warrant, and so leave myself .a-

commutator-plates at the same angular position, are connected to comm utator-plates at a different angular position. This is the case with the well-known Edison armature; and

when my invention is applied to machines having such arinatures I cut away my pol epieces at the places indicated with respect to the coils, and not at the places indicated with respect to the commutator-plates with which such coils are connected.

I have hereinbefore described my invention as applicable to a machine having a single horseshoe field-magnet and a ring-armature. My invention 13 not, however, restricted to such a machine, but is applicable to'o'ther 'types of macl1inenamely, to any two or four cuit, as is, for example, the well-known Gramme armature. It is to be understood, however, that though my invention is not applicable to machines having many poles, still, should the diameter of the armature be large, the number of such poles might be increased to, say, six or eight. In the case of such types of machine as I have just indicated I proceed as hereinbefore described that is, I take readings enabling me to plot out shaping-curves, and afterward remove the metal as shown to be necessary by such shapingcurves.

In order to explain more clearly the application of my invention in the case of other known types of machine, aforesaid, I shall proceed to consider what the action of single horseshoe-magnets must be upona ring-armature in order that there may be no sparking at the brushes whatever may be their position on the commutator. It will be understood that in a single horseshoe field-magnet as usually constructed the magnetism of the pole-pieces at the part nearest the field-magnet coils is stronger than at the part most remote therefrom; therefore, as the current is taken 01f the armature at different positions with respect to the two polepieccs-in one of them nearer the field-magnet coils and in. the other farther away from them (see Fig. 3)t-h.e shaping-curves indicated with respect to the two pole-pieces will differ from one another, as will the shape of the part to be cut away from each pole-piece. This will be readily seen by reference to the two shapingcurves shown, respectively, above and below the horizontal line in Fig. 1, where they will be seen to differ. In a drurn-armature, as is well known, each coil is simultaneously acted upon by both polc-pieces, so that in exploring after the manner hereinbeiorc n'icnt-ioncd round one half of the field I would in reality have explored both halves oi the field, and the diagram I would take "would only be onehalf of such a'one as is shown in Fig.1. The

shaping-cuiwe would indicate the resultant eifect of both pole-pieces on onecoil; and in carrying my invention int-o effect I might either cut away one pole-piece only or cut away both to such an extent that the sum of the grooves cut in them would equal the groove cut in one pole-piece only.

By the employment of pole-pieces cut" away or incised, as hereinbefore specified, together with a suitable device for altering the position' of the brushes, I am able, when the machine is used as a generator, to maintain a constant current through a variable resistance, or a constant current or elect-ro-mot'ive force when the machine is driven at varyin g speeds, and when the machine is used as a motor to vary the mechanical energy given out. 7

It is not necessary that separate shapingcurves should be obtained for every individual machine constructed, for one shapingcurve will apply to all machines made to one pattern; but any alteration of pattern that would sensibly alter the strength of the field, such as an alteration in the windingof the field-magnets or'armature, would entail the 'obtaining of a new shapingcurve and the cutting away or incision of thepole-pieces in accordance therewith.

Having thus specified the nature of my in-' vention and the best manner of carrying it into effect with which I am acquainted, I

would add that modifications of amechanical nature may be introduced without departing from the essence-of my invention. For example, one might bore a number of small holes through or to a certain depth into the pole-piece orcut a number of horizontal channels or grooves along its face, the said holes or channels being deepest or widest or most numerous at the part from which the shaping-curve shows that the largest amount of metal has to be excised. such a nature would readily suggest themselves to an ingenious mind; but they would be mere self-evident variations of the invention heieinlmlore set forth.

I am aware that before this date pole-pieces have been modified in form for various purposes. For example, modified forms which maybe looked upon as polepieces of ordinal type cut away or incised have been described by Houston and Thompson, by Trouv, by \Vissendanger, by Vieston, by Joel, by Lever, and by E. and J. I'IOPkiHSOIhflHd J. Platttbut such modified forms of pole-piece as they describe difter essentially from mine and have diii'erent objects in view. I therefore desire it to be understood that I make no claim to the methods of modifying pole-pieces which they describe.

I desire it to be understood that in this SjdlBCiilOttlOll I make no claim to the generic or specific forms of pole-piece embodying my invention, as I. .claim such in the specification accompanying a separate application for a Modifications of IIO patent, which application was filed at the United States Patent Olfice onv February 9, 1888, and received the Serial No. 263,453.

Having fully described my invention, what- I claim, and desire to secure by Letters Patent, iS' Y r 1. The method of determining the shape of the pole-pieces of dynamo-electric machines or motors, consisting of exploring the armature at various points around the same under different positions of the commutator-brushes the pole-pieces of dynamoelectric machinesv at the point indicated by the curve so Ob t ained, then replotting the curve, and again or motors,iconsisting, first, in obtaining a curve which represents the excess of induction over self-induction, then removing experimentally less metal than required from the pole-pieces experimenting until suflicient'correction be obtained to make the inductive eife'ct equal to the self-inductive eflect.

3. The method of determining the shape of the pole-pieces of a dynamo-electric machine or motor to prevent sparking when the,

brushes are shifted, which consists in" plot ting out exploration-curves obtained in sub-- stantially the manner described, setting up ordinates corresponding to the various positions of the commutator-brushes in their several positions, and joining-by aline the points where, these ordinates out their respective curves.- I 4'. The method, as hereinbefore set forth, of

determining the shapeof the pole-pieces of a dynamo-electric machine or-motor to vary the magnetic efiect of said pole-pieces. upon said armature'and render the magnetic effect of said pole-pieces on said armature equal to the self-induction generated in the coils of the armature passing under the brushes at the time to prevent sparking, which consists in running said dynamo or, motor under normal conditions, placing the brushes at several points around the commutator and measuring the difierences of potential between adjacent coils around the armature for each position ofthe brushes, plotting the curves of said differences of potential by setting out the angular distances around the commutator as abscissae and the differences of potential as ordinates for every position of the brushes, erecting ordinates corresponding :to the angles at which-the brushes are located in the several positions, noting the points where these ordinates cut their curves and joining the points so located by-"a line the angular position, size, and form of which will indicate the position, shape, and proportionally the amount of metal to be cut from the pole-- pieces. i

5. The method of determining the shape of the polepieces of dynamo-electric machines or motors-to prevent sparking when the brushes are shifted, which consists inrunniug said dynamo or motor with a constant current. and resistance, or a variable load, respectively, changing the position of the brushes around the commutator, measuring the difference of potential between the adjacent coils around the commutator to c0rre spend with each position of the brushes, plot-' ting the curves of said difie'rences of, potential, setting out ordinates corresponding with the various positions of the brushes and noting the points where the said ordinates cut their corresponding curves, joining the points so located by a line and constructing the polepieces to correspond with the position and.

shape of "this line and substantially in-p'ro'-..

' portion to thear'ea-inclosed by said line, then running the dynamo under normal condi tions' again and shifting the brushes asbefore, measuring the diiferences of potential.

between theadjacent coils around the arma ture as before, and shaping the pole-pieces until the curves representing the difierences of potential .in adjacent coils'cut the zeroline of said cu'rves' =a t points corresponding to the location of saidbrushes.

JOHN GRIOE STA'lTER.

Witnesses:

JAMES GRIEVELORRAIN,

CHARLES JOHN HOWELL THOMAS. 

